Integration of Synchronous Condensers into the Transmission System

The increase in renewable energy generation in northern Germany and the simultaneous shutdown of nuclear and coal fired power plants mainly in the south has various impacts on the German 400 kV transmission system. To cope with the increasingly high and volatile power flows, the transmission system needs to be reinforced and reactive power compensation devices (e.g., synchronous condensers, STATCOM) need to be implemented. Rapidly changing power flows as well as the increasingly volatile reactive power exchange with the distribution grid are directly reflected in the voltage profile of the transmission system. To date, nuclear and fossil fired power plants have been played a decisive role for voltage control and reactive power provision in the highly loaded transmission system. The gradual shutdown of these power plants leaves behind a serious gap that needs to be compensated by other technologies. The objective of this paper is to describe aspects of the integration of synchronous condensers into the transmission system. The main design, control concepts and performance of recently connected synchronous condensers are discussed and illustrated by means of simulation studies and measurements.

I. Introduction

The voltage in the 400 kV AC transmission system must be kept within narrow limits, both in normal operation and in the event of faults. Too low voltages bear the danger of a voltage collapse (voltage instability [1], [2]), whereas too high voltages can damage equipment or cause it to shut down.